The invention relates to iron complexes soluble in organic media, usable as catalysts in various chemical reactions, and particularly as additives for improving the combustion of liquid fuels. It also concerns the preparation of such complex compounds.
It is known that various iron complexes soluble in organic media are used as combustion adjuvants for liquid fuels, a domain where, among the economical and ecological aims, priority is given to the attempts made to save energy and to reduce pollution. Interest in the improvements which can be brought to the efficiency of these combustion adjuvants is thus fully understood.
The combustion of liquid hydrocarbons, such for example as gas-oils, fuel oils or still kerosine oil, leads, even under the optimum economic conditions, to the emission, to a certain extent, of unburnt solid, liquid or gaseous substances, such as, for example as soot, cracked hydrocarbons, carbon monoxide as well as nitrogen oxides. These unburnt substances have the main disadvantages of lowering the yield of the power generators (fuel oil burners, Diesel engines etc . . . ) due to the loss of combustible material and the formation of deposits (mainly soot) on the heat exchangers, which results in a decrease of the heat transfer coefficient, and leads to the emission of noxious fumes which must be eliminated as much as possible. Generally, an attempt is made to obviate these disadvantages by incorporating in the liquid fuels (gas-oils or fuel-oils, for example) iron, calcium or barium compounds soluble in organic media, for example, having the effect of preventing the emission of smokes or at least of reducing their amount. These compounds, by catalytic effect, produce a more complete combustion of the fuels and, accordingly, reduce the weight of the solid combustion residues.
Various methods for manufacturing such complexes soluble in organic media have already been described, particularly in U.S. Pat. Nos. 3,891,401 and 3,897,470 and in French Pat. No. 2,172,797.
More particularly, in French Pat. No. 2,172,797, iron organic complexes soluble in organic media are prepared by a process wherein an organic (carboxylic) acid or an organometalloidic (sulfuric, sulfonic or phosphoric) acid having from 8 to 30 carbon atoms, is reacted with ferric hydroxide either freshly prepared, or prepared in situ by reaction of a base with a ferric salt. The reaction between the organic or organometalloidic acid and the ferric hydroxide takes place particularly in the presence of a hydrocarbon solvent, such as naphtha. The French Pat. No. 2,172,797 specifically illustrates in its examples the preparation of additives soluble in organic media from various organic or organometalloidic acids (oleic acid, fatty acids of "tall oil," (dinonyl-phenoxy) phosphoric acid and dodecylbenzene sulfonic acid) and describes, as the resultant products, complexes soluble in organic media wherein the ratio of the number of acid equivalents of the organic or organometalloidic acid to the number of iron atoms has the values of 1/2.9; 1/3 and 1/4.2. These values correspond to relatively low iron ratios with respect to the organic or organometalloidic acid involved.